1. Field of the Invention
This invention concerns transporting large diameter solids through pipelines. More specifically, it concerns transportation of coal in mine size pieces having diameters of greater than 2 inches.
2. General Discussion of the Background
It has been long been known that coal can be transported through pipelines in the form of finely ground particles suspended in a slurry. U.S. Pat. Nos. 2,791,472, 3,517,969, 3,637,263, 4,305,688, 4,436,528, 4,492,589, 4,502,868, 4,507,022 all disclose methods for transporting coal by first reducing it to finely ground particles and suspending it in a transport medium. All of these methods suffer the common defect, however, of greatly increasing the apparent viscosity of the coal by grinding it into small diameter particles which exposes more surface area of the solid. This increase in apparent viscosity makes it more difficult to pump the slurry through a pipeline, thereby substantially increasing energy requirements for transportation. These increases are passed on to consumers of electrical energy in the form of higher electric utility rates. The high apparent viscosity is not fundamentally necessary, but rather is necessitated by current mechanical pump designs which require grinding and pulverization of the coal.
Transportation of coal in the form of fine particles has many other disadvantages. The fine particles adsorb more liquid thereby making it difficult to separate the vehicle from the coal at the pipeline terminus. When the coal is later burned to produce electrical energy, the water must first be evaporated from the coal which thereby reduces the net yield of energy from the product. The slurry of fine particles is also a non-Newtonian liquid.
Yet another problem with finely ground particulate matter is that it is easily carried away by the wind after separation from the vehicle. Attrition by wind and other environmental influences once again increases the cost of energy and has the additional drawback of causing serious environmental pollution.
One of the reasons that prior art methods pumped small diameter particles was the size limitation imposed by the centrifugal or piston pumps that were used. These pumps were inherently incapable of pumping large diameter solids without damaging the pumps. An additional problem caused by these pumps was the introduction of turbulence into the pipeline which decreased the efficiency of flow and tended to degrade any lubricants which had been mixed into the vehicle to reduce friction. In addition, conventional valve designs may not permit proper seating with large diameter chunks.
In prior art pipelines, the velocity at which the coal slurries could be transported was also limited to a narrow range, thereby reducing the ability to send portions of the slurry through the shunt lines to potential markets at branch points en route.
Another problem encountered in prior art pipelines was the difficulty of initially mixing the vehicle and coal at points of pipeline origination or remobilization.
It is accordingly an object of this invention to create a mixture which is a Newtonian liquid with a relatively low apparent viscosity. This goal is achieved by increasing diameter of the solids. In turn, it is an object of this invention to minimize flow losses with the reduced viscosity.
Another object of the invention is to reduce the apparent viscosity and frictional loss of energy during transportation of mixtures.
Yet another object of the invention is to decrease turbulence within the pump and pipeline to thereby increase energy efficiency and reduce degradation of lubricants added to the mixture.
Still another object of the invention is to provide a method in which the coal or other solids can be easily mixed with a vehicle and separated therefrom at a termination point.
Another object of the invention is to provide a method in which the solid such as coal can be easily remobilized for transshipment.
Finally, it is an object of the invention to provide a method of pumping coal in which shunt lines can be employed for transportation of the slurry to remote locations off the main pipeline.